US EPA

29716 

Technical Report 

Carcinogenicity of Kevlar aramid pulp following intraperitoneal injection into rats 

Davis, JMG 

1987 

NIOSH/00175443 

Roxburgh Place 

TM/87/12 

The aromatic polyamide fiber Kevlar was tested to assess the carcinogenicity of this material which is being used to replace asbestos. Kevlar pulp consists of fibers ranging from 0.5 to 8 millimeters in length. However, due to abrasion processes, fibrils can be peeled from the surface of large fibers which will then be of respirable length. Material suitable for injection was prepared and injected intraperitoneally into AF-rats at dose levels of 25, 2.5, or 0.25mg/kg. No difference in survival was noted when treated rats were compared to control rats. Cellular reaction to the fibrils was vigorous with large cellular granulomas developing in which the injected Kevlar was embedded. The granulomas consisted mainly of macrophages and fibroblasts but also held many foreign body giant cells. Eventually fibrosis developed and both collagen and reticulin were identified. Peritoneal mesotheliomas were found in two of 32 rats in the group receiving the highest dose. The author concludes that the Kevlar preparation has a low, but definite carcinogenic potential. Airborne fibers may be of even smaller size than those injected in this study and therefore of greater carcinogenic potential. According to the author, levels of such airborne fibers should be investigated in the workplace and means sought to keep this exposure to the lowest possible level.